Involvement of a gelsolin-related protein in spermatogenesis of the earthworm Lumbricus terrestris

Abstract

A gelsolin-related protein was isolated from seminal vesicles of the annelid Lumbricus terrestris. Compared with the isoforms of the gelsolin-related protein previously found in the muscle of the annelid body wall, the isolated protein was assigned to the first isoform (EWAM-P1) because of its electrophoretic mobility, chromatographic elution behaviour, immunological cross-reactivity and identical nucleotide sequence of segments obtained by reverse transcription/polymerase chain reaction. Immunofluorescence studies with smear preparations of developing male germ cells revealed characteristic changes of the local distribution of actin and EWAM-P1 during spermatogenesis. These changes were correlated with the developmental transport processes and structural alterations. F-actin, as revealed by rhodamine-phalloidin staining, formed a toroid-shaped structure in cytoplasmic bridges connecting the germ cells to a central cytophore during the developmental stages. An actin antibody reacting with both G- and F-actin demonstrated that actin was concentrated at the proximal and distal parts of the spermatocytes. EWAM-P1 was also localized in these regions, with intense staining in the distal part of spermatocytes and young spermatids in which the Golgi complex and proacrosome resided. The anti-actin antibody further stained the periphery of the nucleus. This staining gradually reduced during sperm maturation and covered about half of the length of the nucleus in elongated spermatids. Co-localization of EWAM with actin implied a functional significance of this gelsolin-related protein for the rearrangement of the actin cytoskeleton during earthworm spermiogenesis.

Formation of germ-line cysts with a central cytoplasmic core is accompanied by specific orientation of mitotic spindles and partitioning of existing intercellular bridges

“…Simultaneously dividing germ cells have repeatedly been observed during spermatogenesis ( Fig. 2a- d;Fernández et al 1992;Krüger et al 2008). In female cysts, the synchrony of mitoses may be lost at different phases of their development, as observed in T. tessulatum and P. geometra (this study; not shown).…”

“…The testes in Clitellates contain clusters of gonial cells (cystocytes). In leeches (Hirudinea), spermatogenesis is confined to male gonads (Fernández et al 1992), whereas in oligochaetous clitellates, cystocyte clusters still at the initial stages of their differentiation are transferred from testes into seminal vesicles in which the germ cells undergo further divisions, enter meiosis and then pass through the subsequent phases of spermiogenesis (Ferraguti 1999;Jamieson 2006;Krüger et al 2008). Development of the male germ-cell clusters is not synchronous and so clusters at various stages of mitotic divisions, meiosis and spermiogenesis can be observed (Fernández et al 1992;Ferraguti 1999;Jamieson 2006; this study).…”

“…In all clitellate species, each cystocyte in the cluster is connected to a central cytophore via its own intercellular bridge (Fernández et al 1992;Jamieson 2006;Krüger et al 2008;Siekierska 2003;Świątek 2005a, 2005b, 2008Fig. 1a-d).…”

“…The number of cystocytes per cluster in male cysts is usually high, e.g. 128 germ cells in Lumbricus terrestris (Krüger et al 2008) and 256 in H. medicinalis (Fernández et al 1992 The orientation of mitotic spindles, both relative to the cytophore and to each other, can be reliably visualized only by the analysis of whole-mount preparations immunostained to localize mitotic spindle markers (e.g. β-tubulin, Fig.…”

An ultrastructural study of the ovary cord organization and oogenesis in Erpobdella johanssoni (Annelida, Clitellata: Hirudinida)

“…These cysts have a characteristic spatial arrangement; each germ cell in a given cyst has only one RC connecting it to a common anuclear cytoplasmic mass -the cytophore. Numerous studies have shown that the formation of germline cysts with a central cytophore is a conserved phase of gametogenesis in Clitellata (Fernández et al, 1992;Ferraguti, 1999;Jamieson, 2006;Krüger et al, 2008;Spałek-Wołczyńska et al, 2008;Swiątek, 2005bSwiątek, , 2008Świątek et al, 2009Ben Ahmed et al, 2010) and should be regarded as a primary condition (Urbisz et al, 2010;Świątek et al, 2012). Similar germline cysts with a central cytoplasmic mass have been found during gametogenesis in some Polychaeta, Plathyhelmintes and Nematoda (Sawada, 1975;Hirsh et al, 1976;Foor, 1983;Gibert et al, 1984;Sopott-Ehlers, 1989).…”